From: Igmar Palsenberg <igmar@palsenberg.com>
To: musl@lists.openwall.com
Subject: Re: malloc(0) behaviour
Date: Tue, 15 Jan 2013 23:28:14 +0100 [thread overview]
Message-ID: <A85FE2D1-89CB-4892-8696-AD5477582B57@palsenberg.com> (raw)
In-Reply-To: <20130115134802.GY20323@brightrain.aerifal.cx>
>>
>> That's there to access if size is 0 ? Sure, you can access :
>>
>> struct foo {
>> };
>
> This is a constraint violation. C does not allow empty structs, and
> even if it did, they would not have size 0, since no type or object
> ever has size 0 in C.
GCC thinks otherwise :
#include <stdlib.h>
#include <stdio.h>
struct test {
};
int main(int argc, char **argv)
{
char *x = NULL;
printf("sizeof test : %d\n", sizeof(struct test));
return 0;
}
[igmar@devel ~]$ ./x
sizeof test : 0
It gives me a warning, but doesn't error out. Olders version might behave differently, I don't have those installed. The LLVM compiler does the same.
No idea what the standard says, but your remarks sounds correct to me.
>>
>> which is size 0. I do wonder what that gives me in practice. That is, not counting the fact that :
>>
>> if (size == 0)
>> size = 1;
>>
>> was a common practice in malloc() implementations a while ago.
>
> Of course, this is the canonical, simplest way to make malloc(0)
> return a unique pointer.
Enough for this thread. I did got the answer I wanted, and the result I want is easy to realise. Not mu intention to irritate people.
Igmar
next prev parent reply other threads:[~2013-01-15 22:28 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-14 17:17 Igmar Palsenberg
2013-01-14 18:05 ` Rich Felker
2013-01-14 22:22 ` Strake
2013-01-14 23:05 ` Rich Felker
2013-01-15 8:32 ` Igmar Palsenberg
2013-01-15 12:53 ` Rob Landley
2013-01-15 22:18 ` Igmar Palsenberg
2013-01-15 8:31 ` Igmar Palsenberg
2013-01-15 11:06 ` Szabolcs Nagy
2013-01-15 12:33 ` Igmar Palsenberg
2013-01-15 13:48 ` Rich Felker
2013-01-15 22:28 ` Igmar Palsenberg [this message]
2013-01-15 23:22 ` Rob
2013-01-16 7:46 ` Igmar Palsenberg
2013-01-15 13:46 ` Rich Felker
2013-01-15 12:52 ` Rob Landley
2013-01-14 23:37 ` Rob Landley
2013-01-15 0:24 ` Rich Felker
2013-01-15 12:17 ` Rob Landley
2013-01-15 9:01 ` Igmar Palsenberg
2013-01-15 12:58 ` Rob Landley
2013-01-15 14:54 ` dladdr() pierre
2013-01-15 18:48 ` dladdr() Rich Felker
2013-01-16 11:00 ` dladdr() pierre
2013-01-16 12:51 ` dladdr() Szabolcs Nagy
2013-01-16 14:24 ` dladdr() musl
2013-01-16 15:20 ` dladdr() pierre
2013-01-16 16:49 ` dladdr() Rich Felker
2013-01-16 17:42 ` dladdr() musl
2013-01-21 2:03 ` dladdr() Rich Felker
2013-01-21 6:58 ` dladdr() pierre
2013-01-21 18:35 ` dladdr() Rich Felker
2013-01-22 6:27 ` dladdr() pierre
2013-01-22 13:07 ` dladdr() Szabolcs Nagy
2013-01-22 13:40 ` dladdr() pierre
2013-01-22 13:51 ` dladdr() Rich Felker
2013-01-22 14:59 ` dladdr() pierre
2013-01-22 16:11 ` dladdr() Szabolcs Nagy
2013-01-22 23:43 ` dladdr() Rich Felker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=A85FE2D1-89CB-4892-8696-AD5477582B57@palsenberg.com \
--to=igmar@palsenberg.com \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).